Reading a Mortgage Amortization Schedule
An amortization schedule is 360 rows of the same payment split differently every month. Once you see the pattern, the loan stops being mysterious.
Each payment covers that month's interest on the remaining balance, and the rest reduces principal. Early payments are mostly interest; late payments are mostly principal. The schedule is fixed at origination for fixed-rate loans, which is why extra principal payments are so powerful early.
The monthly split
Month 1 on a $300,000, 7 percent loan: interest = $300,000 x 0.07/12 = $1,750. Payment $1,996 leaves $246 for principal. Month 2: interest on $299,754 = $1,748.57, principal $247.43. The principal slice grows by the interest saved each month, compounding quietly for 30 years.
The crossover point
Somewhere around year 22 of a 30-year loan at typical rates, the principal portion finally exceeds the interest portion. Before that, you are mostly renting money; after it, you are mostly buying the house. Extra payments move the crossover earlier, which is the whole game.
Fixed vs adjustable schedules
A fixed-rate schedule never changes: same payment, same math, all 360 months. An adjustable-rate loan re-amortizes at each reset, so the schedule is really a series of mini-schedules. That is why ARM borrowers should model the worst-case reset, not just the teaser payment.
What the schedule does not show
Escrow (taxes, insurance, PMI) is not part of amortization math; it rides alongside the payment and changes yearly. The schedule also assumes on-time payments: late fees and missed months are not in the table.
Skip the arithmetic
See your own payoff timeline with and without extra payments.
Amortization questions
What is a mortgage amortization schedule?
An amortization schedule lists every payment on the loan, showing how much of each goes to interest versus principal and the remaining balance after each month.
Why is so much of my early payment interest?
Because monthly interest equals the annual rate divided by 12 times the remaining balance, and the balance is biggest early. As principal shrinks, the interest slice shrinks with it.
Does an amortization schedule change?
For fixed-rate mortgages the schedule is locked at origination. Adjustable-rate mortgages generate a new schedule at each rate adjustment.
Where do extra payments show on the schedule?
The original schedule assumes minimum payments. Extra principal payments shorten the real timeline below what the schedule shows; that is exactly what this calculator models.